POSITION SENSOR FOR A TIMEPIECE SETTING STEM
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Abstract
A capacitive sensor to determine instantaneous angular position of a rotatable element in a timepiece, such as a setting stem of a wristwatch. Static electrodes are configured to form, in conjunction with rotor electrodes of the rotatable element, a first differential capacitance pair and a second differential capacitance pair. A sensor calculation unit is configured to sense difference values from the differential capacitances pairs and to evaluate the angular position of the rotatable element from the difference values using predetermined information relating the differential capacitance values to angular position values.
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Citations
27 Claims
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1-15. -15 (canceled)
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16. A capacitive sensor for determining an instantaneous angular position of a rotatable element of a timepiece, the capacitive sensor comprising:
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six stator electrodes formed as concentric arcs segments centered on the axis of rotation of the rotatable element, the first, third, fourth and sixth stator electrodes extending along 45°
, and the second and fifth stator electrodes extending along 135°
, the first and second, respectively the second and third, the fourth and fifth, and the fifth and sixth stator electrodes, extending along a common 45-degree angular portion, the four 45-degree angular portions being distinct;one rotor electrode configured to rotate with the rotatable element, the rotor electrode being made of two identical parts extending symmetrically on either side of its rotation axis along 90°
;the rotor electrode and the stator electrodes configured to, during a rotation cycle of the rotatable element, provide capacitances between two of the six stator electrodes, such that each of the capacitances varies over at least a portion of the rotation cycle due to the influence of the rotor electrode; the capacitances comprising a first differential capacitance pair comprising a first capacitance formed between the first and second stator electrodes, and a second capacitance formed between the second and third of stator electrodes, the first capacitance having an instantaneous first capacitance value X1 and the second capacitance having an instantaneous second capacitance value X2 depending on the angular positioning of the rotor electrode; the capacitances comprising a second differential capacitance pair comprising a third capacitance formed between the fourth and fifth stator electrodes, and a fourth capacitance formed between the fifth and sixth stator electrodes, the third capacitance having an instantaneous third capacitance value X3 and the fourth capacitance having an instantaneous fourth capacitance value X4 depending on the angular positioning of the rotor electrode; the capacitive sensor comprising a sensor driver circuit for sensing capacitance values X1, X2, X3 and X4, and for determining the instantaneous angular position by evaluating a first differential capacitance value X1−
2=X1−
X2 and a second differential capacitance value X3−
4=X3−
X4. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification